Hard surfacing of mineral fiber



M. R. xlMNEz HARD SURFAGING OF MINERAL 'FIBER Filed Aug. 1942 PatentedJam, 1946 Amum sUnFAcING oF MINERAL man Manuel R. Ximenez, Plaineld, N.J., assigner to Johns-Manvllle Corporation, New York, N. Y., a.corporation of New York Application August 4, 1942, Serial No. .453,567

2 Claims.

The present invention relates to thermal insulation and, moreparticularly, to the hard surfacing and reinforcing of mineral woolinsulation to adapt it for lining the walls and ceilings of buildings,the hulls of ships, and for similar purposes where mechanical strengthand a marresistant and attractive external surface is desired, togetherWithflreand heat-resistance, low` thermal conductivity, and moderateflexibility.

The heat insulating properties of mineral wool insulation result fromthe insulating eiiect of the dead air which is trapped in the pores orinterstices between the loosely associated mineral bers. Since thethermal conductivity of this material is inversely proportional to itsdensity, a mineral fiber batt or felted sheet of a shape and sizeconvenient for application to a surface to be insulated possesses verirlow mechanical strength and is easily compressed and compacted, withresulting loss of insulating value.

An object of the present invention is to pro-- vide a composite body ofmineral ber insulation which shall have a continuous, hard, strong,flameproof, decorative, thin and flexible external suriace layer ofrelatively low thermal conductivity, superposed on and attached toa'mechanically weak, relatively thick mineral wool batt of highinsulation efficiency.

Another object of the invention is `to provide a thin insulating coversheet for mineral 4wool batts or felted sheets with suillcient strengthand rigidity to support and maintain the mineral fibers in theiroriginal porous, high insulating.

condition and having sufficient flexibility to a1- low application ofthe composite unit by cementing. `nailing, or other suitable fasteningto moderately curved, as Well as flat, wall surfaces.

Another object of the invention is to provide such a cover for mineralber batts and felts which is waterand grease-resistant, possesses highheat stability, and provides a surface suiciently adherent to permitcementing to the underlying batt and to permit application thereto ofilnishing coats of paint, enamel, varnishes or lacquers.

Still another object of the invention is to provide a hard surfacingcover for mineral wool batts and felts, possessing suiiicient toughnessto resist marring by flexing, compression and punc.-l

ture strains, and providing suiilcient reinforcing strength to protectthe composite articleagainst damage in handling and service and to adaptit for structural purposes.

In order to strengthen mineral wool bats with.. out substantiallydetracting from the high heat insulating properties thereof, one featureof the present invention contemplates use of asbestos paper laminates of2 to 4 ply thickness bonded with thermo-setting resin as the preferredreinforcing cover of the composite insulating element. A.thermosettingresin is necessary to impart strength and heat stability to thecomposite element. A phenol-formaldehyde type of thermosetting resin isthe preferred bonding agent for the asbestos paper `laminate because. cithe inherent high strength and chemical and heat stability of laminatesbonded therewith. However,

ordinary laminatesbonded by conventional methods with thermo-settingphenolic resins have certain undesirable characteristics, such asbrittleness, inammability, high oost, and possession of a surfacabolthbefore and after curing, which aiiords no adherent base either forcements or for flninshing coats of paint, enamel, or varnish.

Such characteristics of phenol#formaldehyde--` bonded laminates wouldmilitate against their use in a product and process of the presentinvention, were it not for the discovery that by limiting the proportionof phenolic resin bonding agent with which the asbestos paper laminateis impregnated within very low and deiinite proportions, and byplasticizing the resin with a compara-tively high proportion oftri-cresyl phosphate flameprooflng and ilexibilizing agent, it ispossible to produce a reinforcing cover with all of the desirablecharacteristics heretofore mentioned.

A still further object of the invention is to provide a simple andeconomical method of p'roducing strong and flexible 2 to 4 ply asbestospaper laminates bonded with iiameproofedv phenolic resins in amountsadjusted to provide hard surfaces which afford an adherent base forcements, paints, and enamels.

With the above and other objects and features in view, the inventionconsists in the improved method oi hard surfacing mineral fiberinsulation, and in the vproduct ithereby produced, as hereinafterdescribed and more particularly defined in the accompanying claims.

In the following description reference will be A the element has beenslightly nexed -to conform to a curved surface.

The reinforcing and surfacing element of the composite thermalVinsulation forming the .subject of this invention preferably comprises athin 2 to 4 ply asbestos paper laminate, bers, I0 oi' which are bondedwith not to exceed 25% by weight of the paper of a flameproofed andplasti. cized thermo-setting phenolic resin I2. The asbestos paper maybe reinforced with vegetable nbers, such as cotton scrim, and, in somecases an asbestos ber millboa'rd containing up to 20% of its weight ofan inorganic silicate (for example, calcium silicate) bond may replacethe asbestos paper as the fiber base oi' the reinforcing element oi thecomposite insulation unit,

y A preferred method of impregnatlng the asbestos paper with thephenolic resin is by immersion of the paper in a solvent solution of theresin. A suitable resin solution for this purpose mayl for example,consist of approximately 24% "A stage phenol-formaldehyde resin,approximately 8% hexamethylenetetramine, approximately 51/2% tri-cresylphosphate plasticizer, and approximately 671/2% ethyl alcohol solvent.The "A stage phenol-formaldehyde resin is preferably proportioned to thetri-cresyl phosphate within the limits of 80%-85% resin to 15%20%tricresyl phosphate in the impregnant solution. 'I'he proportion ofsolvent in the impregnant solution preferably lies within the range 60%'70% by weight of the impregnant.

The impregnating operation is carried on in such a way as to produce afinished, bonded asbestos sheet containing resin and plasticizer inproportions withln the range 20%25% oi the weight of the paper.

As previously indicated. phenolic resins are.

the preferred bonding agents because they are characterized by highchemical and heat stability and high bonding strength or adhesion. Thephenolic resin component of the impregnant may be partially orcompletely replaced by a thermo setting natural resin of the gumaccroides type, but gum accroides do not provide as4 strong or adherentbonds as do the phenol-formaldehyde resins.

In preparing the asbestos paper laminates, as well as in impregnating asingle ply asbestos asbestos paper sheet or asbestosi'iber millboard,impregnation is carried out by immersion of the asbestos sheet ormillboard in the resin-plasticizer solution. A thin asbestos paper sheetcan be suitably impregnated within a period of about 20 seconds, and theimpregnation time for thicker materials may extend up to 5 minutes.vAfter removal from the impregnation solution, the impregnated sheet ispassed through a wringer, doctor knives, or press rollers to squeeze outexcess impregnant. The impregnated sheet is tlien subjected to a dryingoperation for removal of solvent. Either air drying or oven drying maybe employed, the oven being operated at a temperature of from 150 F. to200 F. The dry resin-impregnated sheets leaving the drier are then builtup or otherwise assembled to form a 2 to 4 ply asbestos laminate, whichisthen subjected to a' heat and pressure cure atv a temperature in therange 325-350 F. and under a pressure of 700-900 lbs. per square inch.The heat and pressure curing of thus-impregnated'Z to 4 ply laminates,can be completed within a period of 10 to 20 minutes. A single plyasbestos thus impregnated can also be cured by 3 minutes pressing, or bysets of hot calendering rolls.

4comparatively low impregnant in the thus heat-cured asbestos paperproduct, the hardened surface Ny of the paper presents an adherent basefor cements and iinishing coats of paints, enamels, and varnishes. Itis, therefore, possible to amx the heat-cured asbestos paper laminate toa mineral wool batt or felt i6 by a suitable cement I8, such aswaterproofed casein glue or adhesives of the type of celluloseiether oralkyd-resin emulsions. The preferred cement is one which will set up inthe cold, does not require the use of organic solvents, hascomparatively high viscosity and low penetration oi porous surfaces suchas mineral wool batts. The cement should also develop a permanent set,possess moisture and heat stability,

and have a high degree of flexibility. In aillxing the resin-impregnatedasbestos paper laminate cover to a mineral wool batt, an alkyd-resinemulsion, diluted with water to suitable consistency, may be eitherbrushed, sprayed, or rolled on one surface o the laminate sheet, and themineral ber batt is then applied on thethus-coated laminate surface. Thecoated surface and the batt may be pressed together, as by steel platesor other weights, rollers, hinged screen frames, etc., to provide a goodcontact between the coated surface and the batt while the cement isdrying. The cement will set; in a few hours at room temperature, and thecementlng action can be completed within a period of 20 minutes inconveyor ovens heated up to 350V F.

The last step in the manufacture of the composite insulation unit mayadvantageously oonsist in applying a baking paint or enamel 20 to theexposed surface of the reinforcing laminate sheet. This enamelingoperation can be readily completed under baking temperatures, since thelaminate sheet, and also the cement employed in attaching the laminateto the mineral ber batt,

can readily stand baking temperatures as high ing the laminates abovedescribed, they can be g made much more siimply` and economically thanpossible with a conventional laminating process. For example, themaximum molding pressures employed in making the laminates yof thepresent invention are from 700 to 900 lbs. per square inch, which isbelow the minimum limit oi' molding pressure employed in conventional*practice.

Standard laminating practice requires the presence of small amounts ofvolatile constituents such as solvents and others. The presence of theseis one oi' the reasons for the cooling o1 the laminating sheets withinthe molding press to avoid development of blisters by liberation ofvapors. The residual volatile constituents are required to keep theimpregnated sheets :flexible enough for handling (the sheets would bebrittle if bone dry), and, secondarily, to promote the flow oi' theresin under heat and pressure, the resulting tackiness causing theconsolidation of the sheets. According to the method 0i' thepresproportion of phenolic resin ent invention, both flexibility andtackiness un-l der heat aresecured by the presence of the nonvolatiletri-cresyl phosphate plasticizer, and, accordingly, the impregnatedsheets are non-tacky but flexible, even when dry. Consequently, noresidual solvent is required during the pressure molding operation. Thetackiness under heat disappears as soon as the resin is curedy but thecured laminated sheet retains flexibility. A single ply, cured,impregnated asbestos paper sheet retains sufficient flexibility so thatit can be wound on a one inch diameter mandrel.

Since, according to the present process, the impregnated laminates canbe cooled after removal` from the molding press, (preferably Whileconfined under weights or mechanical pressure, as by stacking betweenplates used in lamination),- the press time required for treatment underheat is only about one-half the press time required in conventionalpractice for effecting heat and pressure cure, followed by cooling underpressure. The presence of tri-cresyl phosphate in the cured sheetsprovides a lubricant allowing removal of the laminates from the presswhile hot at the end of the short curing cycle. When phenolic resinimpregnated laminates are cooled Within the lmolding press after theheat and pressure cure has been completed, the laminate is more brittlethan one of comparable composition which has been cooled after removalfrom the press. '.Ihe thus prolonged period of high temperature to whichthe. laminate is exposed during slow curing within the press has aweakening and embrittling effect on any reinforcing cotton fibers, andthis prolonged high temperature exposure also tends to promote stickingof the laminates and breaking down of asbestos fiber bundles under thepressure of the press. This tendency to develop sticklness tends toincrease when molding pressures above 1,000 lbs. per square inch areemployed. Such high pressures cause excessive.

flow of resin, and this excessive resin now also tends to break downasbestos fiber and reinforcing cotton scrim.

As previously indicated, resin-bonded laminates, even phenolic resinbonded asbestos paper or asbestos cloth laminates, are not name-` proof.The phenol-formaldehyde resin impregnants normally contain nofire-retardants and, even worse, they may contain a small percentage ofa drying oil. The laminated asbestos paper sheets of the presentinvention require the presence of a high percentage of plasticizer inthe bond, and the preferred plasticizer, tri-cresyl phosphate, is one ofthe best fire-retardant liquid plasticizers available. l

The surfaces of fiber paper laminates which have been bonded withphenol-formaldehyde resin by conventional impregnation methods' are ofsuch smooth texture that they have no adhesion for paint or otherfinishes or for cement. The only Way that such laminates can beconsolidated with, and cemented to, other suri faces, such as in themanufacture of presswood, is by effecting the consolidation under heatand pressure, and after special treatment such as a vto any surface,either before or after curing; and

the surfaces thereof can be attractively finished with any of the commonwater, oil, or synthetic resin paints, varnishes, or enamels'by anymethod of application and without any bleeding effect.

If conventional methods of high pressure moldingwere employed in themanufacture of the-thin 2 to 4 ply asbestos paper laminates of thepresent invention, using conventional high proportions of resin, theheavy flow of resin developed at conventional molding heats andpressures would have the effect of breaking the bond between theasbestos paper and any reinforcing scrim, with resulting distortion ofthe asbestos paper-scrim laminate. On the other hand, asbestos paperlaminates (with or without scrim or fiber reinforcement), made at thelower laminating pressures employed in accordance with the presentinvention, and with the lower resin proportions, retain their textureduring the molding and curing operation.

The hard surfaced composite thermal insulation elements which form thesubject of the present invention possess a high degree of mechanicalstrength and resistance to marringor distortion by impact and puncture,while at the same time retaining sufficient flexibility to allow oftheir adaptability to cover curved surfaces, such as ship hulls.Furthermore, the exposed hard surface of composite insulation is adaptedfor taking an attractive finish and can, therefore, serve as the innerwall lining or ceiling for a room or chamber. The impregnated asbestospaper sheet laminate or millboard is Ilameproof, and possesses good heatinsulating value. It is also substantially waterproof, can be renderedcompletely waterproof and washable by a suitable waterproof finish orcoating, and the com'- posite unit therefore possesses and retains itshigh insulation characteristics. The composite unit can be safelyshipped in assembled form and can be conveniently and readily cut tosize to ilt` any specific building operation.

What I claim is:

1. The process of manufacturing a hard surfaced, somewhat lexible facingsheet which comprises, impregnating asbestos ber paper with a. solventsolution of thermo-setting phenolic resin binder plasticized with15%-20% of tri-cresyl phosphate, limiting the amount of plasticizedresin binder retained by the paper within the range 20 %25% by weight ofthe paper, drying the paper to evaporate all the solvent, building up a2 to 4 ply laminate of thus-impregnated sheets, curing the laminate forr10 to 20 minutes at a temperature of 325-350 F. and under a pressure of'10o-900 lbs. per square inch, immedi resin containing 15-20% by Weightof tricresyl phosphate, and the individual plies of said resinimpregnated paper having sufcient flexibility to withstand Winding on aone-inch diameter mandrei.

. MANUEL R. XIMENEZ.

